Unlike an iPad-like tablet, Wacom offers several different lines and models. Let's first take a look at the technology and hardware that's common to all of the tablets to grasp exactly how a Wacom tablet functions.
We really have to start with the pen; Wacom refers to the pen's system as Penabled Technology. Sure, it looks like a regular pen but inside lurks a digital chip, a modulator and a transmitter. All of those components work in a complicated manner, but we can break it down: The tip of the pen tells the tablet what to do. And it's done with magnets! Well, not exactly. The sensor board of the tablet has a magnetic field, and the pen produces its own magnetic field -- and energy -- from it. (That's why no batteries or power adapter is needed.)
The magnetic field emanating from the pen is recognized by the sensor board. From that, it can track the pen's location, pressure and speed. The sensor board itself is made up of a lot of little antenna coils, but it also has a control board that monitors the coils to determine where the current is (i.e., where the pen is). And that's what tells your computer that you want to add a moustache to the picture of your sister that you're photoshopping. Wacom calls this patented technology EMR, or electromagnetic resonance technology.
It's a little different if an LCD screen is used, which is the case with the Cintiq line of tablets. In that case, backlighting or a component that gives off its own field could disrupt the pen's magnetic field. As such, all metal or problem parts must be tightly shielded to block out the field. The metal frame around the LCD screen -- which undoubtedly affects magnetic fields -- is accounted for in the control board, which recognizes a "weak" signal from the pen and corrects it so it follows a predictive course.